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Biological Applications (biological + application)
Selected AbstractsCONTROL ISSUES IN HIGH-SPEED AFM FOR BIOLOGICAL APPLICATIONS: COLLAGEN IMAGING EXAMPLEASIAN JOURNAL OF CONTROL, Issue 2 2004Q. Zou ABSTRACT This article considers the precision positioning problem associated with high-speed operation of the Atomic Force Microscope (AFM), and presents an inversion-based control approach to achieve precision positioning. Although AFMs have high (nanoscale) spatial resolution, a problem with current AFM systems is that they have low temporal resolution, i.e., AFM imaging is slow. In particular, current AFM imaging cannot be used to provide three-dimensional, time-lapse images of fast processes when imaging relatively-large, soft samples. For instance, current AFM imaging of living cells takes 1,2 minutes (per image frame) , such imaging speeds are too slow to study rapid biological processes that occur in seconds, e.g., to investigate the rapid movement of cells or the fast dehydration and denaturation of collagen. This inability, to rapidly image fast biological processes, motivates our current research to increase the operating speed of the AFM. We apply an inversion-based feedback/feedforward control approach to overcome positioning problems that limit the operating speed of current AFM systems. The efficacy of the method, to achieve high-speed AFM operation, is experimentally evaluated by applying it to image collagen samples. [source] Multifunctional Mesoporous Silica Material Used for Detection and Adsorption of Cu2+ in Aqueous Solution and Biological Applications in vitro and in vivoADVANCED FUNCTIONAL MATERIALS, Issue 12 2010Qingtao Meng Abstract An inorganic,organic silica material (SBA,P2), prepared by immobilization of the 1,8-naphthalimide-based receptor P2 within the channels of the mesoporous silica material SBA-15, is characterized by transmission electron microscopy and several spectroscopic methods. SBA,P2 features a high affinity Cu2+ -specific fluorescence response in aqueous solution with a detection limit for Cu2+ of ca. 0.65,ppb (10,×,10,9,M) under optimized conditions. It can extract Cu2+ from the solution with only trace amounts remaining. Through isolating of the toxic ions within the mesopores of the silica, SBA,P2 has the potential to work as a toxicide for Cu2+ in living systems. The fluorogenical responses are reversible and do not vary over a broad (4.0 to 9.0) pH range suitable for application under physiological conditions. The fluorescence responses of Cu2+ in vitro (human breast cancer cells) and in vivo (five-day-old zebrafish) demonstrate the possibility of further application in biology. [source] Selective Zinc(II)-Ion Fluorescence Sensing by a Functionalized Mesoporous Material Covalently Grafted with a Fluorescent Chromophore and Consequent Biological ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 2 2009Krishanu Sarkar Abstract A highly ordered 2D-hexagonal mesoporous silica material is functionalized with 3-aminopropyltriethoxysilane. This organically modified mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4-methyl-2,6-diformyl phenol. Powder X-ray diffraction, transmission electron microscopy, N2 sorption, Fourier transform infrared spectroscopy, and UV-visible absorption and emission have been employed to characterize the material. This material shows excellent selective Zn2+ sensing, which is due to the fluorophore moiety present at its surface. Fluorescence measurements reveal that the emission intensity of the Zn2+ -bound mesoporous material increases significantly upon addition of various concentrations of Zn2+, while the introduction of other biologically relevant (Ca2+, Mg2+, Na+, and K+) and environmentally hazardous transition-metal ions results in either unchanged or weakened intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Zn2+, evident from the large binding constant value (0.87,×,104M,1). Thus, this functionalized mesoporous material grafted with the fluorescent chromophore could monitor or recognize Zn2+ from a mixture of ions that contains Zn2+ even in trace amounts and can be considered as a selective fluorescent probe. We have examined the application of this mesoporous zinc(II) sensor to cultured living cells (A375 human melanoma and human cervical cancer cell, HeLa) by fluorescence microscopy. [source] Synthesis of a Far Red Absorbing Thiobarbituric Acid Oxonol Derivative as a Fluorescent Probe for Biological ApplicationsCHEMINFORM, Issue 16 2004Leslie W. Deady Abstract For Abstract see ChemInform Abstract in Full Text. [source] Polymeric Actuators for Biological ApplicationsCHEMPHYSCHEM, Issue 12 2007Avishay Pelah Dr. Abstract To shed light on the role of cell rheology and mechanotransduction in various physiological and disease states, different techniques of force application, such as optical tweezers and deformable substrates, are employed. In this present paper we describe a new approach for the deformation of cells based on the temperature-sensitive polymer poly(N-isopropylacrylamide), PNIPAM. In response to temperature changes, PNIPAM gels undergo extensive and reversible changes in volume that allow them to be used as actuators for stretching and compressing cells and tissues. Herein we focus mainly on our experience with the deformation of red blood cells as proof of principle, and demonstrate the wealth of possibilities such stimuli-responsive materials may offer as actuators. [source] Solid-state NMR Structure DeterminationIUBMB LIFE, Issue 9 2003Alison Drechsler Abstract Biological applications of solid-state NMR (SS-NMR) have been predominantly in the area of model membrane systems. Increasingly the focus has been membrane peptides and proteins. SS-NMR is able to provide information about how the peptides or proteins interact with the lipids or other peptides/proteins in the membrane, their effect on the membrane and the location of the peptides or proteins relative to the membrane surface. Recent developments in biological SS-NMR have been made possible by improvements in labelling and NMR techniques. This review discusses aligned systems and magic angle spinning techniques, bilayers and bicelles, and measurement of chemical shift anisotropy and dipolar coupling. A number of specific experiments such as cross polarization, rotational resonance, REDOR, PISEMA, MAOSS and multidimensional experiments are described. In addition to 2H, 13C and 15N, recent solid-sate 1H, 19F and 17O NMR work is discussed. Several examples of the use of SS-NMR to determine the structure of membrane peptides and proteins are given. IUBMB Life, 55: 515-523, 2003 [source] Polyelectrolyte complex hydrogel composed of chitosan and poly(,-glutamic acid) for biological application: Preparation, physical properties, and cytocompatibilityJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Hahk-Soo Kang Abstract Polyelectrolyte complex (PEC) hydrogels composed of chitosan as a cationic polyelectrolyte and poly (,-glutamic acid) (,-PGA) as an anionic polyelectrolyte were prepared from PEC dispersions based on a chitosan solution to which different amounts of ,-PGA solutions were added to charge equivalency. The chemical structures of the PEC hydrogels were investigated by Fourier transform infrared spectroscopy. The physical properties, fixed charge concentration, crystallinity, mechanical properties, micromorphology, and swelling properties of the PEC hydrogels were also investigated. The total fixed charge concentration of the PEC hydrogels varied as a function of pH on the pK intervals between chitosan (pK = 6.5) and ,-PGA (pK = 2.27). The isoelectric points (IEP) were shifted to a lower pH with a higher weight ratio of ,-PGA to chitosan. The elastic modulus was decreased with the weight ratio increasing from 0 : 1 to 1 : 1 (,-PGA/chitosan) by ionic crosslinking between the amino groups of chitosan and the carboxyl groups of ,-PGA. The results of the swelling study showed that the swelling properties of PEC hydrogels were more affected by the change in the elastic restoring force than by the change in the fixed charge concentration depending on the pH. Also, the cytotoxicity of the PEC hydrogels was investigated using normal human dermal fibroblast (NHDF) cell lines, and the results showed the PEC hydrogels were not toxic. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:386,394, 2007 [source] Synthesis and biological application of glycopolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2007Yoshiko Miura Abstract Saccharides on the cell surfaces participate in a number of biochemical phenomena via the protein,saccharide interaction. Synthetic glycopolymers mimic the function of the cell-surface saccharides and efficiently interact with proteins, cells, and pathogens based on the multivalent effect. Since the biological functions of saccharides are paid much attention, the glycopolymers are being increasingly explored as biomaterials for medicinal application and tissue engineering. This review presents a practical approach of glycopolymers. The glycopolymers were prepared by the facile syntheses of poly(vinyl saccharide)s and the physical and biological properties were introduced. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5031,5036, 2007 [source] Synthesis and utilization of E. coli -encapsulated PEG-based microdroplet using a microfluidic chip for biological applicationBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2010Kyoung G. Lee Abstract We report herein an effective strategy for encapsulating Escherichia coli in polyethylene glycol diacrylate (PEGDA) microdroplets using a microfluidic device and chemical polymerization. PEGDA was employed as a reactant due to the biocompatibility, high porosity, and hydrophilic property. The uniform size and shape of microdroplets are obtained in a single-step process using microfluidic device. The size of microdroplets can be controlled through the changing continuous flow rate. The combination of microdroplet generation and chemical polymerization techniques provide unique environment to produce non-toxic ways of fabricating microorganism-encapsulated hydrogel microbeads. Due to these unique properties of micro-sized hydrogel microbeads, the encapsulated E. coli can maintain viability inside of microbeads and green fluorescent protein (GFP) and red fluorescent protein (RFP) genes are efficiently expressed inside of microbeads after isopropyl- , - D -thiogalactopyranoside induction, suggesting that there is no low-molecular weight substrate transfer limitation inside of microbeads. Furthermore, non-toxic, gentle, and outstanding biocompatibility of microbeads, the encapsulated E. coli can be used in various applications including biotransformation, biosensing, bioremediation, and engineering of artificial cells. Biotechnol. Bioeng. 2010;107:747,751. © 2010 Wiley Periodicals, Inc. [source] A Practical Gold-Catalyzed Route to 4-Substituted Oxazolidin-2-ones from N -Boc PropargylaminesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2007Eun-Sun Lee Abstract AuI -catalyzed cyclization of N -Boc propargylamines into 4-alkylidene oxazolidin-2-ones is described. This modularapproach provides access to a variety of nonproteogenic 4-substituted oxazolidinones that are important in asymmetric synthesis and biological applications. The current flexible route is characterized by low catalyst loading, mild conditions, and operational simplicity.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Design of Multiresponsive Hydrogel Particles and AssembliesADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Grant R. Hendrickson Abstract In the realm of soft nanotechnology, hydrogel micro- and nanoparticles represent a versatile class of responsive materials. Over the last decade, our group has investigated the synthesis and physicochemical properties of a variety of synthetic hydrogel particles. From these efforts, several particle types have emerged with potentially enabling features for biological applications, including nanogels for targeted drug delivery, microlenses for biosensing, and coatings for biomedical devices. For example, core/shell nanogels have been used to encapsulate and deliver small interfering RNA to ovarian cancer cells; nanogels used in this fashion may improve therapeutic outcomes for a variety of macromolecular therapeutics. Microgels arranged as multilayers on implantable biomaterials greatly minimize the host inflammatory response to the material. Furthermore, the triggered release of drugs (i.e., insulin) has been demonstrated from similar assemblies. The goal of this feature article is to highlight developments in the design of responsive microgels and nanogels in the context of our recent efforts and in relation to the community that has grown up around this fascinating class of materials. [source] Upconverting Nanoparticles: The Active-Core/Active-Shell Approach: A Strategy to Enhance the Upconversion Luminescence in Lanthanide-Doped Nanoparticles (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 18 2009Mater. Lanthanide-doped nanoparticles capable of (up)converting near-infrared (NIR) light to higher energies via an anti-Stokes process known as upconversion have demonstrated extraordinary potential in biological applications on the virtue that background fluorescence is near-zero. To maximize the intensity of the upconverted luminescence in lanthanide-doped nanoparticles, Vetrone et al. utilize a core/active-shell architecture where the active-shell readily absorbs NIR light and transfers it to the active luminescent core, thereby increasing the upconversion emission, as described on page 2924. [source] Diamond Transistor Array for Extracellular Recording From Electrogenic CellsADVANCED FUNCTIONAL MATERIALS, Issue 18 2009Markus Dankerl Abstract The transduction of electric signals from cells to electronic devices is mandatory for medical applications such as neuroprostheses and fundamental research on communication in neuronal networks. Here, the use of diamond with its advantages for biological applications as a new material for biohybrid devices for the detection of cell signals is investigated. Using the surface conductivity of hydrogen-terminated single-crystalline diamond substrates, arrays of solution-gate field-effect transistors were fabricated. The characterization of the transistors reveals a good stability in electrolyte solutions for at least 7 days. On these devices, cardiomyocyte-like HL-1 cells as well as human embryonic kidney cells (HEK293), which were stably transfected with potassium channels, are cultured. Both types of cells show healthy growth and good adhesion to the substrate. The diamond transistors are used to detect electrical signals from both types of cells by recording the extracellular potential. For the HL-1 cells, the shape of action potentials can be resolved and the propagation of the signal across the cell layer is visible. Potassium currents of HEK293 cells are activated with the patch-clamp technique in voltage-clamp mode and simultaneously measured with the field-effect transistors. The ion sensitivity of the diamond surface enables the detection of released potassium ions accumulated in the cleft between transistor and cell. [source] Generic Method of Preparing Multifunctional Fluorescent Nanoparticles Using Flash NanoPrecipitationADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Mustafa Akbulut Abstract There is increased demand for nanoparticles with a high fluorescence yield that have the desired excitation wavelength, surface functionalization, and particle size to act as biological probes. Here, a simple, rapid, and robust method, Flash NanoPrecipitation (FNP), to produce such fluorescent nanoparticles is described. This process involves encapsulation of a hydrophobic fluorophore with an amphiphilic biocompatible diblock copolymer in a kinetically frozen state. FNP is used to produce nanoparticles ranging from 30 to 800,nm with fluorescence emission peaks ranging from, but not limited to, 370,nm to 720,nm. Such fluorescent nanoparticles remain stable in aqueous solutions, and, in contrast to soluble dyes, show no photobleaching. Fluorophores and drugs are incorporated into a single nanoparticle, allowing for simultaneous drug delivery and biological imaging. In addition, functionalization of nanoparticle surfaces with disease-specific ligands permits precise cell targeting. These features make FNP-produced fluorescent nanoparticles highly desirable for various biological applications. [source] Advanced silicon microstructures, sensors, and systemsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2007Oliver Paul Non-Member Abstract This paper presents the progress in silicon-based biomedical microstructures, material characterization techniques, and mechanical microsystems by the authors' research team. Microneedle and microelectrode arrays with fluidic through-wafer vias and electrical contacts were developed. The structures are designed for dermatological and biological applications such as allergy testing, surface electromyography, and spatially resolved impedance spectroscopy. The characterization of thin films has relied on the bulge test. By the formulation of more powerful models, the application range of the bulge test was extended to elastically supported thin-film multilayers. This enables the mechanical properties of thin films to be determined reliably. Finally, progress in the operation and application of novel stress sensors based on CMOS diffusions and field effect transistors and exploiting the pseudo-Hall effect is reported. Their integration into powerful single-chip microsystems is described. Applications include stress mapping, force and torque measurements, and tactile surface probing of microcomponents. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Assembling DNA into Advanced Materials: From Nanostructured Films to Biosensing and Delivery Systems,ADVANCED MATERIALS, Issue 21 2007Abstract The past decade has witnessed a rapid expansion in the design and assembly of engineered materials for biological applications. However, such applications place limitations on the molecular building blocks that can be used. Requirements for polymer-based building blocks include biocompatibility, biodegradability, and stimuli-responsive behavior. Many traditional polymers used in materials science are limited in at least one of these areas, so new polymers need to be explored. As we outline here, DNA is one such polymer that shows promise in developing the next generation of ,smart' materials for biomedical and diagnostic applications. [source] Functional modification of poly(vinyl alcohol) through phosphorus containing nitrogen heterocyclic moietiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008S. Karpagam Abstract Functional modification of poly(vinyl alcohol) (PVA) with phosphorus containing nitrogen heterocyclic has been believed to have extensive thermal and biological applications in the area of polymers. Efforts have been taken for the synthesis of phosphorus-containing N -heterocyclic (5,6 member and fused ring) based PVA. The synthesized compounds were characterized using UV, FTIR, and NMR spectral studies. Thermal studies (DSC-TGA) scans display phosphorus-containing five membered and fused heterocyclic-based PVA has less thermal stability than six-membered compounds. Modified polymers infer to have excellent bacterial response against micro-organisms. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Interfacial formation of porous membranes with poly(ethylene glycol) in a microfluidic environmentJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Dongshin Kim Abstract In a microfluidic environment, the liquid,liquid interface, formed by laminar flows of immiscible solutions, can be used to generate thin membranes via interfacial polymerization. Because these thin nylon membranes have a very small pore size or lack porosity entirely, their utilization in some biological applications is greatly limited. We introduce an in situ fabrication method using the interfacial reaction of a two-phase system to generate a porous nylon membrane. The membranes were characterized with scanning electron microscopy and fluorescent beads. Scanning electron microscopy micrographs verified the asymmetrical structure of the porous membrane, and the membrane pore sizes ranged from 0.1 to 1 ,m. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008. [source] Synthetic strategies in the construction of chromonesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2010Nian-Guang Li Because of important biological applications of chromones, some synthetic strategies leading to more complex derivatives have been widely explored in the past years. Thus, the purpose of this review is to report some recent improvements of the classical synthetic methods and of some nonclassical methods to obtain simple oxygenated chromones. The strategies for synthesis of heterocycle analogs containing phosphorus, nitrogen, and sulfur are also summarized. J. Heterocyclic Chem., (2010). [source] Modern MALDI time-of-flight mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2009Marvin L. Vestal Abstract This paper focuses on development of time-of-flight (TOF) mass spectrometry in response to the invention of matrix-assisted laser desorption/ionization (MALDI). Before this breakthrough ionization technique for nonvolatile molecules, TOF was generally considered as a useful tool for exotic studies of ion properties but was not widely applied to analytical problems. Improved TOF instruments and software that allow the full potential power of MALDI to be applied to difficult biological applications are described. A theoretical approach to the design and optimization of MALDI-TOF instruments for particular applications is presented. Experimental data are provided that are in excellent agreement with theoretical predictions of resolving power and mass accuracy. Data on sensitivity and dynamic range using kilohertz laser rates are also summarized. These results indicate that combinations of high-performance MALDI-TOF and TOF-TOF with off-line high-capacity separations may ultimately provide throughput and dynamic range several orders of magnitude greater than those currently available with electrospray LC-MS and MS-MS. Copyright © 2009 John Wiley & Sons, Ltd. [source] Gel-free sample preparation for the nanoscale LC-MS/MS analysis and identification of low-nanogram protein samplesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2007Marco Gaspari Abstract Protein identification at the low nanogram level could in principle be obtained by most nanoscale LC-MS/MS systems. Nevertheless, the complex sample preparation procedures generally required in biological applications, and the consequent high risk of sample losses, very often hamper practical achievement of such low levels. In fact, the minimal amount of protein required for the identification from a gel band or spot, in general, largely exceeds the theoretical limit of identification reachable by nanoscale LC-MS/MS systems. A method for the identification of low levels of purified proteins, allowing limits of identification down to 1 ng when using standard bore, 75 ,m id nanoscale LC-MS/MS systems is here reported. The method comprises an offline two-step sample cleanup, subsequent to protein digestion, which is designed to minimize sample losses, allows high flexibility in the choice of digestion conditions and delivers a highly purified peptide mixture even from "real world" digestion conditions, thus allowing the subsequent nanoscale LC-MS/MS analysis to be performed in automated, unattended operation for long series. The method can be applied to the characterization of low levels of affinity purified proteins. [source] Metallogenomics and biological X-ray absorption spectroscopyJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2005Isabella Ascone An overview of the second special issue of the journal on biological applications of X-ray absorption spectroscopy (BioXAS) is presented. The emphasis is on the study of metalloproteins in the context of structural genomics programmes (metallogenomics). [source] Theory of Ca L2,3 -edge XAS using a novel multichannel multiple-scattering methodJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2005Peter Krüger A new method for calculating X-ray absorption spectroscopy (XAS) at the L2,3 edges of Ca and transition metals is presented. It is based on the multichannel multiple-scattering theory by Natoli et al. [Phys. Rev. B, (1990), 42, 1944,1968] combined with the eigen-channel R-matrix formalism. Atomic multiplet-like effects, owing to the Coulomb interaction of photoelectrons and the 2p hole, are taken into account through a configuration interaction ansatz for the final-state wavefunction. The various multiplet states lead to a set of channels for the photoelectron wavefunction, which is calculated in multiple-scattering theory. The method is applied to Ca, an important element for biological applications of XAS. An L:L branching ratio of 3:4 is found, in good agreement with experiment but in contrast to the statistical value 2:1 obtained in all one-electron approaches. By using a linear mixture between statically screened (,90%) and unscreened (,10%) core-hole potential, the line shape, too, agrees well with the experimental one. [source] Introductory overview: X-ray absorption spectroscopy and structural genomicsJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2003Isabella Ascone A special issue of the journal is presented, dedicated to biological applications of X-ray absorption spectroscopy (BioXAS) and examining the role of this technique in post-genomic biology. The issue confirms that BioXAS has come of age and it can be expected to make a significant contribution in the structural genomics effort on metalloproteins, which are estimated to make up about 30% of proteins coded by genomes. [source] X-Ray laser: past, present, and futureLASER PHYSICS LETTERS, Issue 6 2009S. Suckewer Abstract In this review we concentrate our attention on X-ray laser research and development covering the so called soft X-ray region (down to , 10 nm) and the "water window" region (down to 2.3 , 4.4 nm). We present the development of soft X-ray lasers (SXLs) and their applications using primarily collisional and recombination schemes. We present the paths towards compact systems and major achievements to date. We discuss conditions for using both schemes to reach the "water window" region. In this discussion we also present another possible schemes based on photo-pumping, inner shell transitions in atoms and ions and "Doppler Compression" of IR laser radiation down to the X-ray region with its intrinsic tunability possibility. A significant part of the review is dedicated to the wide range of applications of SXLs with wavelengths at and above 10 nm. Also discussed is the potential of extending the range of biological applications for the "water window" region. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Upconversion: road to El Dorado of the fluorescence worldLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 4 2010Li Ching Ong Abstract Upconversion nanoparticles (UCNs), in the recent times have attracted attention due to their unique properties, which makes them ideal fluorophores for use in biological applications. There have been various reports on their use for targeted cell imaging, drug and gene delivery and also for diffuse optical tomography. Here we give a brief introduction on what are UCNs and the mechanism of upconversion, followed by a discussion on the biological applications of UCNs and further on what the future holds for UCNs. Copyright © 2010 John Wiley & Sons, Ltd. [source] Nanotube Friendly Poly(N -isopropylacrylamide)MACROMOLECULAR RAPID COMMUNICATIONS, Issue 15 2010Krishna C. Etika Abstract Poly(N -ispropylacrylamide) [PNIPAM] is a widely studied polymer for use in biological applications due to its lower critical solution temperature (LCST) being so close to the human body temperature. Unfortunately, attempts to combine carbon nanotubes (CNTs) with PNIPAM have been unsuccessful due to poor interactions between these two materials. In this work, a PNIPAM copolymer with 1,mol-% pyrene side group [p-PNIPAM] was used to produce a thermoresponsive polymer capable of stabilizing both single and multi-walled carbon nanotubes (MWNTs) in water. The presence of pyrene in the polymer chain lowers the LCST less than 4,°C and the interaction with nanotubes does not show any influence on LCST. Moreover, p-PNIPAM stabilized nanotubes show a temperature-dependent dispersion in water that allows the level of nanotube exfoliation/bundling to be controlled. Cryo-TEM images, turbidity, and viscosity of these suspensions were used to characterize these thermoresponsive changes. This ability to manipulate the dispersion state of CNTs in water with p-PNIPAM will likely benefit many biological applications, such as drug delivery, optical sensors, and hydrogels. [source] Carbon blacks as EPR sensors for localized measurements of tissue oxygenationMAGNETIC RESONANCE IN MEDICINE, Issue 6 2004Minbo Lan Abstract New electron paramagnetic resonance (EPR) oximetry probes were identified in the class of carbon black materials. These compounds exhibit very high oxygen sensitivity and favorable EPR characteristics for biological applications. At low pO2, the linewidth is particularly sensitive to changes in oxygen tension (sensitivity of 750 mG/mmHg). The application of the probes for oximetry was demonstrated in vivo: the pO2 was measured in muscle in which the blood flow was temporarily restricted as well as in tumor-bearing mice during a carbogen breathing challenge. The responsiveness to pO2 was stable in muscle for at least 3 months. No toxicity was observed using these materials in cellular experiments and in histological studies performed 2, 7, and 28 days after implantation. In view of their EPR characteristics (high sensitivity) as well as the well-characterized production procedure that make them available on a large scale, these probes can be considered as very promising tools for future developments in EPR oximetry. Magn Reson Med 51:1272,1278, 2004. © 2004 Wiley-Liss, Inc. [source] Molecular Contrast Optical Coherence Tomography: A Review,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2005Changhuei Yang ABSTRACT This article reviews the current state of research on the use of molecular contrast agents in optical coherence tomography (OCT) imaging techniques. After a brief discussion of the basic principle of OCT and the importance of incorporating molecular contrast agent usage into this imaging modality, we shall present an overview of the different molecular contrast OCT (MCOCT) methods that have been developed thus far. We will then discuss several important practical issues that define the possible range of contrast agent choice, the design criteria for engineered molecular contrast agent and the implementability of a given MCOCT method for clinical or biological applications. We will conclude by outlining a few areas of pursuit that deserve a greater degree of research and development. [source] Highly sensitive spin-valve devices for chip-cytometersPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2009Jong Wook Roh Abstract The highly sensitive spin-valve devices integrated with a microfluidic channel have been studied for cell counting in a chip-cytometer. The presence or absence of a single magnetic bead was successfully detected by direct measurement of fringe fields emanating from magnetic beads using spin-valve devices. The real-time detection was also successfully confirmed by the direct measurement of magnetic fields generated from the magnetic beads passing an active sensing area of a spin-valve device integrated with a microfluidic channel. Our results show the possibility of implementing a chip-cytometer for biological applications using the highly sensitive spin-valve devices integrated with a microfluidic device. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||||||||||||||||||||